The present invention relates to an image forming apparatus.
In an image forming apparatus which uses the electrophotographic system, conventionally, a photosensitive member which is an image carrier is charged by a charging device, the charged photosensitive member is irradiated with light corresponding to image information to form a latent image, the latent image is developed by a developing device, and the developed toner image is transferred to a recording medium to form an image.
In accordance with advancement of the image colorization, a tandem color image forming apparatus having plural image forming units for respectively performing image forming processes has been proposed. In such apparatus, color toner images including a cyan image, a magenta image, a yellow image, and preferably a black image are formed on respective photosensitive members, and the toner images are overlaid and transferred to an endless intermediate transfer member in transferring positions of the photosensitive members, thereby forming a full-color image.
Such a tandem color image forming apparatus has the image forming units for respective colors, and hence is advantageous in enhancing the speed.
Hereinafter, a conventional tandem color image forming apparatus will be described.
FIG. 11 is a diagram showing the configuration of a conventional color image forming apparatus.
Referring to FIG. 11, in a main unit 1 of the color image forming apparatus, image forming units 2, 3, 4, and 5 for respectively forming toner images of yellow (Y), magenta (M), cyan (C), and black (K) are placed. Exposing devices 6a, 6b, 6c, and 6d are disposed so as to respectively correspond to the image forming units 2 to 5. The image forming units 2 to 5 comprise: photosensitive drums (photosensitive members) 2a, 3a, 4a, and 5a which are irradiated with laser beams emitted from the exposing devices 6a to 6d to form electrostatic latent images on their peripheral faces; developing rollers (developing sections) 2b, 3b, 4b, and 5b which cause toners supplied from respective toner tanks to adhere to the photosensitive drums 2a to 5a, thereby developing the electrostatic latent images as toner images; and cleaning blades which remove away toners that remain on the photosensitive drums 2a to 5a after the image transfer.
An endless intermediate transfer belt (intermediate transfer member) 7 to which the developed color toner images on the photosensitive drums 2a, 3a, 4a, and 5a are to be overlaid and transferred to form a color toner image is placed below the image forming units 2 to 5 so as to be runnable in the direction of the arrow. In a loop of the intermediate transfer belt 7, a driving roller 8, a tension roller 9, four first transfer rollers 10a, 10b, 10c and 10d, and a driven roller 11 are arranged.
A sheet supply cassette 13 in which sheets (recording media) P are housed is disposed in a lower portion of the apparatus. The sheets P are fed one by one from the sheet supply cassette 13 to a sheet transport path by a sheet feed roller.
A second transfer roller 12 which is in contact with a given distance of the outer peripheral face of the intermediate transfer belt 7 in the position of the driven roller 11, thereby transferring the color images on the intermediate transfer belt 7 to the sheet P, and a fixing device 14 which fixes the color images transferred onto the sheet P, to the sheet P are placed on the sheet transport path.
The photosensitive drums 2a to 5a of the image forming units 2 to 5 cause the yellow, magenta, cyan, and black toner images to attach to the surface of the intermediate transfer belt 7, thereby forming color images. The toner color images are transferred to the sheet P fed from the sheet supply cassette 13, by a nip force exerted between the driven roller 11 and the second transfer roller 12. The sheet P is then fed to the fixing device 14, and the toner image is fixed thereto. Thereafter, the sheet is discharged.
In the color image forming apparatus, each of the above-mentioned cleaning blades is formed by a body portion configured by an elastic plate member, and a planar base plate portion to which the body portion is secured. The base plate portion is directly secured to a case of the apparatus by screws (for example, see Japanese Patent Publication JP-A-2002-006705).
In the configuration of the conventional art, the cleaning blades must be secured by using screws. Therefore, the workability of the assembly process is impaired.
The cleaning blades are secured by passing the screws through holes formed in the cleaning blades. Consequently, it is difficult to ensure the dimensional accuracy between the cleaning blades and the respective photosensitive drums.